To investigate the effects of ammonia in ACFA on the ash mortar and concrete, measurements of several properties for concrete where 10 ~ 15 % of the cement was replaced with ACFA containing ammonia concentration of from 0 to 620 ppm were carried. Test results showed that compressive strength of concrete was decreased with increasing a replaced amount of ACFA for the cement as well as ammonia concentration in ACFA, due to impacts of aggressive ammonium and sulfate ions. Relative dynamic elastic modulus of concrete containing 15% ACFA for cement was lower to that of no-fly ash concrete. As ammonia concentration in ACFA, and a replaced amount for cement in concrete were increased, the relative dynamic elastic modulus of concrete was decreased indeed.